Pipe welds require periodic reinspection in critical applications, such as in nuclear power stations, and remote control is often required for inspection in order to minimize risk to the operating personnel. The inspecting instrument is usually an ultrasonic transducer moving around and in conductive contact with the pipe adjacent the weld area. The design of remote controlled equipment for carrying this instrument around bends in the piping has presented difficulties and various designs have been proposed, as, for example, in U.S. Pat. No. 4,383,448 and European Patent Application Nos. 0065262 published Nov. 24, 1982, and 0081214 published June 15, 1983. However, there has been a continuing need for an improved design for this purpose, combining improved operation capability with simplified construction.
The use of couplant fluid for ultrasonic transmission between transducer and pipe has also presented difficulties in this application. If the fluid is not replenished during use the performance of the transducer will suffer, but replenishment is complicated by the necessary movement of the transducer around the pipe weld. An approach has been made to solving this problem by using a couplant-filled membrane bag that conforms to changing contours and retains all of the couplant. However, this requires changes in the transducer assembly that increase costs, so a need has remained for a better solution.